I’ve recently switched to using synergy to share a single keyboard and mouse between multiple machines. Previously I would log into my desktop machine (which had the biggest amount of screen real-estate) and then RDP into other machines as necessary. Now with synergy I can use a single keyboard and mouse. It was very easy to set up, and can be configured to auto-start when your computer launches or when you log in (altho I leave it on manual). I doubt very much that this is the only offering in this space, but since they keywords are so general it is hard to know what exactly is out there. Quite possibly there will be commercial applications out there with more features (please leave a comment if you know of any as I would be interested in doing a comparison), but synergy is free (GPL) and seems quite adequate. Bruce likes it too.
I use synergy with my laptop as the server and my desktop as the client so I can drive the laptop from the desktop’s mouse. I needed to do a presentation from my laptop that involved RDP’ing back to my desktop, and forgot that I still had synergy running. The screen postions of the desktop and laptop were now swapped, and the mouse movements and clicks became unpredictable to say the least. It took a couple of embarassing minutes till I figure out what was going on….